Abstract: The present invention relates to a technique for processing sensor data in a battery energy storage system (BESS). The present invention collects sensing data of battery cells through a BMS and transmits it in a Modbus TCP manner, wherein a frame of the Modbus communication protocol includes a function code and data, and the present invention also comprises a Modbus server, wherein the function code includes information of a battery cell having a minimum or maximum sensing value and location information in a rack of batteries; and a Modbus client, which is connected to the Modbus server by the Modbus communication protocol and receives the sensing data.